Pachycheles rudis

Stimpson, 1859

thickclaw porcelain crab, big-clawed porcelain crab

Pachycheles rudis is a porcelain crab in the Porcellanidae, commonly known as the thickclaw porcelain crab or big-clawed porcelain crab. It inhabits the East Pacific coast from Baja California to Kodiak, Alaska. The is a that typically occurs in heterosexual pairs and exhibits size-assortative pairing with apparent long-term mate recognition. It is frequently found in crevices, nooks, and interstices, often occupying discarded barnacle shells lined with the bryozoan Alcyonidium.

Thickclaw Porcelain Crab (Pachycheles rudis) by Harriman Alaska Expedition. Used under a Public domain license.

Pronunciation

How to pronounce Pachycheles rudis: /ˌpækɪˈkiːliːz ˈruːdɪs/

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Identification

As a porcelain crab, Pachycheles rudis can be distinguished from true crabs by its flattened body form and reduced fifth pair of legs tucked beneath the . The "thickclaw" or "big-clawed" refers to prominent chelipeds. -level identification within Pachycheles requires examination of morphological details not specified in available sources.

Images

Habitat

Found in crevices, nooks, and interstices in rocky intertidal and shallow subtidal zones. Frequently occupies discarded barnacle shells lined with the bryozoan Alcyonidium, which provide shelter.

Distribution

East Pacific coast from Baja California, Mexico to Kodiak, Alaska, USA.

Diet

, extracting food particles from water using specialized appendages.

Host Associations

Alcyonidium - barnacle shells occupied by the crab
Aporobopyrus muguensis - Bopyrid isopod that inhibits growth and of crab

Life Cycle

Developmental stages include planktonic typical of decapod , followed by settlement and benthic and stages. Specific details of larval development and duration not documented in available sources.

Behavior

Typically occurs in heterosexual pairs that appear to maintain long-term associations. Both sexes exhibit aggression toward strangers of the opposite sex. Males show elevated aggression toward returning mates after separations exceeding 48 hours, suggesting mate recognition with temporal decay. Pair formation involves agonistic interactions, with females appearing in stable pairs. The fits models previously constructed for monogamous Crustacea.

Ecological Role

As a , contributes to and water column processing in rocky intertidal . Occupies empty barnacle shells, potentially influencing shell availability for other organisms.

Similar Taxa

Other Pachycheles speciesCongeneric porcelain crabs with similar ; require detailed examination for separation
Other PorcellanidaeShared characteristics of flattened body and reduced fifth legs; -level features distinguish Pachycheles

More Details

Parasitism effects

The bopyrid isopod Aporobopyrus muguensis parasitizes P. rudis, causing reduced frequency, smaller moult increments, delayed sexual maturity in females, and substantially reduced with smaller size-specific clutches. Because fecundity increases with body size in this , slower growth rates of parasitized females further limit their reproductive output.

Mating system

Strong size correlation between paired crabs suggests long-term pairings rather than random mating. Mate recognition appears to decay after approximately 48 hours of separation, after which resident males treat returning females with aggression comparable to that shown toward strangers.